Camera with color correction after luminance and chrominance separation

ABSTRACT

An apparatus having a circuit is disclosed. The circuit may be configured to (i) receive a digital image from an electro-optical sensor, (ii) convert the digital image from a red-green-blue representation to a luminance-and-chrominance representation, (iii) generate a reduced noise representation of the digital image by reducing noise in the luminance-and-chrominance representation and (iv) generate a color corrected representation of the digital image by color correcting the reduced noise representation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to U.S. Ser. No. 12/727,517, filed Mar. 19,2010, which is related to co-pending U.S. application Ser. No.12/706,816 filed Feb. 17, 2010, and Ser. No. 12/712,307 filed Feb. 25,2010, and U.S. Pat. No. 7,536,487, which are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a method and/or architecture fordigital cameras generally and, more particularly, to a camera with colorcorrection after luminance and chrominance separation.

BACKGROUND OF THE INVENTION

A conventional camera sensor employs filters that pass through red,green, and blue light to different pixels on a sensor. The colormeasured on the sensor (Bayer values) is not the final colorrepresentation used in the picture, as a conventional camera will havethe following steps: (i) black level subtraction, (ii) white balance,(iii) demosaic (generating RGB triples for each pixel from the sensorBayer Color Filter Array (CFA) pattern), (iv) color correction (i.e., athree-dimensional mapping from an input RGB color space to an output RGBcolor space), (v) tone curve (mapping the color from a linear cameraspace to a nonlinear output space—linear means that the amount of lightrepresented by a sample is directly in proportion to a correspondingdigital value) and (vi) conversion from RGB to YUV.

Color correction is commonly used in digital cameras because a spectralresponse of the camera photo-receptors does not match a desired responsein an output color space. The color correction is used to produce apicture that has accurate and aesthetically pleasing colors.Unfortunately, the amplitude of noise, especially in some colors, can begreatly increased by the color correction.

Several conventional color correction methods are currently available.Some methods use a matrix (M) multiplication to calculate an RGB outputvector from a red, green, blue (RGB) input vector, such as:R_out=M11×R_in+M12×G_in+M13×B_inG_out=M21×R_in+M22×G_in+M23×B_inB_out=M31×R_in+M32×G_in+M33×B_inFor example, the Adobe “Digital Negative (DNG) Specifications” fileformat specifies color correction by means of a matrix. Otherconventional color correction methods use a three-dimensional lookuptable, with interpolation between the table entries. For example, U.S.Pat. No. 4,275,413 describes a method for tetrahedral interpolation.

Referring to FIG. 1, a block diagram of a conventional camera colorprocessing pipeline 20 is shown. Noise reduction is conventionally doneat a few of many different points in the pipeline 20. FIG. 1 shown thesix color processing steps mentioned above plus a YUV to YUV colorcorrection step, a compression step and several noise reduction steps. Atypical camera performs noise reduction only in some of the placesillustrated.

Different tradeoffs exist between implementing the noise reduction atdifferent points in the pipeline 20. From a cost point of view, noisereduction is less expensive to implement: (i) before demosaicing asopposed to after demosaicing, (ii) after tone correction as opposed tobefore tone correction and (iii) after conversion to YUV as opposed tojust before conversion to YUV. After demosaicing the data rate istripled. After tone correction fewer bits per sample typically exist.After conversion to YUV, especially if down-sampling to the 4:2:2 formator the 4:2:0 format is involved, the sample rate is often reduced.

From a quality point of view (better quality meaning more noisereduction with fewer or less-objectionable artifacts such as loss ofsharpness and detail) filtering at different places has differentadvantages. For example, filtering early in the processing can beadvantageous because noise has not yet spread between the samples orsignificantly changed. On the other hand, filtering after conversion toYUV can be advantageous because the type and amount of filteringsuitable for chrominance data are different from the type and amount offiltering suitable for luminance data. Typically, the chrominance datais filtered more heavily than the luminance data.

Referring to FIG. 2, a diagram of an example signal amplitude before 22and after 24 a conventional spatial noise filtering is shown. Noisereduction by spatial noise filtering distinguishes between signalvariations that are due to noise versus signal variations that are dueto changes in the underlying signal. Different conventional techniquesjudge (i) small signal variations as noise to be reduced or eliminatedand (ii) large signal variations where the underlying signal is to bemaintained.

Referring to FIG. 3, a diagram of an example signal amplitude before 26and after 28 a conventional color correction is shown. Typically, theamplitude of an observed variation relative to the noise standarddeviation is used to determine if the variation is due to noise orvariation in the underlying signal. As described earlier, colorcorrection can increase noise in some colors. In the diagram, some noise30 is not increased by the color correction while other noise 32 isincreased.

Due to the color-dependent noise amplification, a determination or evenapproximation of the noise standard deviation after color correction canbe difficult or expensive, especially if the color correction process iscomplex. Therefore, the quality of any noise reduction after colorcorrection is usually degraded, for example, noise reduction done afterconversion to YUV. Noise reduction done in YUV may be appropriate forthe reasons described above (i.e., cost and ability to control type andamount of filtering for chrominance independent of luminance). However,the effectiveness of such noise reductions can be degraded by occurringafter the color correction.

SUMMARY OF THE INVENTION

The present invention concerns an apparatus having a circuit. Thecircuit may be configured to (i) receive a digital image from anelectro-optical sensor, (ii) convert the digital image from ared-green-blue representation to a luminance-and-chrominancerepresentation, (iii) generate a reduced noise representation of thedigital image by reducing noise in the luminance-and-chrominancerepresentation and (iv) generate a color corrected representation of thedigital image by color correcting the reduced noise representation.

The objects, features and advantages of the present invention includeproviding a camera with color correction after luminance and chrominanceseparation that may (i) perform color correction after a conversion to aYUV color space, (ii) provide luminance and chrominance noise reductionprior to the color correction, (iii) minimize color-dependent noise,and/or (iv) provide different noise filtering for luminance than forchrominance.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will be apparent from the following detailed description andthe appended claims and drawings in which:

FIG. 1 is a block diagram of a conventional camera color processingpipeline;

FIG. 2 is a diagram of an example signal amplitude before and after aconventional spatial noise filtering;

FIG. 3 is a diagram of an example signal amplitude before and after aconventional color correction;

FIG. 4 is a block diagram of an example implementation of an apparatus;

FIG. 5 is a functional block diagram of an example image processingmethod;

FIG. 6 is a functional block diagram of an example image processingmethod in accordance with a preferred embodiment of the presentinvention; and

FIG. 7 is a functional block diagram of another example image processingmethod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 4, a block diagram of an example implementation of anapparatus 100 is shown. The apparatus (or system) 100 may form a digitalstill camera and/or camcorder. The apparatus 100 generally comprises acircuit (or module) 102, a circuit (or module) 104, a circuit (ormodule) 106, a circuit (or port) 107, a circuit (or module) 108 and acircuit (or module) 110. An optical signal (e.g., LIGHT) may be receivedby the circuit 102. The circuit 102 may generate and present a digitalsignal (e.g., D) to the circuit 104. A synchronization signal (e.g.,SYNC) may also be generated by the circuit 102 and received by thecircuit 104. A sensor control signal (e.g., SCNT) may be generated andpresented from the circuit 104 to the circuit 102. A signal (e.g., OUT)may be exchanged between the circuit 104 and the circuit 108. Thecircuit 104 may generate and present a signal (e.g., VIDEO) through theinterface 107 to a monitor outside the apparatus 100. A command signal(e.g., CMD) may be generated by the circuit 110 and presented to thecircuit 104. A signal (e.g., MEM) may be exchanged between the circuit104 and the circuit 106. The circuits 102 to 110 may be implemented inhardware, software, firmware or any combination thereof.

The circuit 102 may implement an electro-optical sensor circuit. Thecircuit 102 is generally operational to convert the optical imagereceived in the signal LIGHT into the signal D based on parametersreceived in the signal SCNT. The signal D may convey the one or moreoptical images as one or more digital images (e.g., fields, frames,pictures). The signal SYNC generally conveys synchronization informationrelated to the images and the pixels within. The signal SCNT may carrywindowing, binning, read rate, offset, scaling, color correction andother configuration information for use by the circuit 102. The imagesmay be generated having an initial resolution and an initial color space(e.g., a Bayer color space) at an initial data rate. In someembodiments, the circuit 102 may include an image pipeline or otherimage source that supplies source images in the signal D.

The circuit 104 may implement a main circuit. The circuit 104 isgenerally operational to generate the signal OUT by processing theimages received in the signal D. The circuit 104 may be operational togenerate the signal SCNT based on the user selections received throughthe signal CMD. The circuit 104 may load and store data to the circuit106 through the signal MEM. The signal OUT generally comprises a stillimage (e.g., JPEG) and/or a sequence of images (or pictures). The signalVIDEO generally comprises a video signal (e.g., ITU-R BT.601, ITU-RBT.709, ITU-R BT.656-4, H.264/AVC, MPEG-2 or MPEG-4). Other standardand/or proprietary still picture and/or video compression standards maybe implemented to meet the criteria of a particular application.

The circuit 104 generally comprises two or more circuits (or modules)111 a-111 n. Each of the circuits 111 a-111 n may be configured toperform one or more operations on the images to achieve final images inthe signals OUT and VIDEO. Processing of the images may include, but isnot limited to, decimation filtering, interpolation, formatting, colorspace conversions, color corrections, tone corrections, gaincorrections, offset corrections, black level calibrations, whitebalancing, image sharpening, image smoothing, and the like. In someembodiments, the processing may be implemented in whole or in part bysoftware running in the circuits 111 a-111 n. In some embodiments, thecircuit 102 and the circuit 104 may be fabricated in (on) separate dies.In other embodiments, the circuit 102 and the circuit 104 may befabricated in (on) the same die. Additional details of the circuit 104may be found in U.S. Pat. No. 7,536,487, hereby incorporated byreference in its entirety.

The circuit 106 may implement a buffer memory. The circuit 106 isgenerally operational to temporarily store image data (e.g., luminanceand chrominance) for the circuit 104. In some embodiments, the circuit106 may be fabricated as one or more dies separate from the circuit 104fabrication. In other embodiments, the circuit 106 may be fabricated in(on) the same die as the circuit 104. The circuit 106 may implement adouble data rate (DDR) synchronous dynamic random access memory (SDRAM).Other memory technologies may be implemented to meet the criteria of aparticular application.

The circuit 107 may implement a connector. The circuit 107 is generallyconfigured to allow the apparatus 100 to be connected to a television orcomputer monitor. Formats for the circuit 107 may include, but are notlimited to, a component interface, s-video interface, a High-DefinitionMultimedia Interface (HDMI) interface and the like.

The circuit 108 may implement a medium. The medium 108 generallycomprises one or more nonvolatile memory devices capable of storing thesignal OUT. In some embodiments, the recording medium 108 may comprise asingle memory medium. For example, the recording medium 108 may beimplemented as a FLASH memory or a micro hard disk drive (also known asa “1-inch” hard drive). The memory may be sized (e.g., 4 gigabyte FLASH,12 gigabyte hard disk drive). In some embodiments, the recording medium108 may be implemented as multiple media. For example, (i) a FLASHmemory may be implemented and (ii) a tape medium or an optical mediummay be implemented for recording the signal OUT. Other types of mediamay be implemented to meet the criteria of a particular application.

The circuit 110 may implement a user input circuit. The circuit 110 maybe operational to generate the signal CMD based on commands receivedfrom a user. The commands received may include, but are not limited to,a take still picture command, a start recording command, a stoprecording command, a zoom in command and a zoom out command. In someembodiments, the signal CMD may comprise multiple discrete signals(e.g., one signal for each switch implemented in the user input circuit110). In other embodiments, the signal CMD may carry the user enteredcommands in a multiplexed fashion as one or a few signals.

The circuit 102 generally comprises a sensor array 112 and a circuit (ormodule) 114. The array 112 may be operational to convert the opticalimages into a series of values in an analog signal (e.g., A). The valuesconveyed in the signal A may be analog voltages representing anintensity value at a predetermined color for each individual sensorelement of the circuit 112. The circuit 112 may include an electroniccropping (or windowing) capability. The electronic cropping capabilitymay be operational to limit readout of image elements in a window (or anactive area) of the circuit 112. The circuit 114 may be operational toprocess and then convert the analog signal A to generate the digitalsignal D. The circuits 112 and 114 may be implemented in hardware,software, firmware or any combination thereof.

Processing of the electronic images in the circuit 114 may include, butis not limited to, analog gain for color corrections and analog offsetadjustments for black level calibrations. The conversion generallycomprises an analog to digital conversion (e.g., 10-bit). An exampleimplementation of the circuit 102 may be an MT9T001 3-megapixel digitalimage sensor available from Micron Technology, Inc., Bosie, Id. Largeror smaller circuits 102 may be implemented to meet the criteria of aparticular application.

Referring to FIG. 5, a functional block diagram of an example imageprocessing method 120 is shown. The method (or process) 120 may begenerally implemented by the apparatus 100, and in particular, by thecircuit 104. The method 120 generally comprises an optional step (orblock) 122, a step (or block) 124, an optional step (or block) 126, astep (or block) 128, an optional step (or block) 130, a step (or block)132, an optional step (or block) 134, a step (or block) 136, an optionalstep (or block) 138, a step (or block) 140, a step (or block) 142, astep (or block) 144, a step (or block) 146 and a step (or block) 148.

The method 120 generally includes processing of the digital images up toan including luminance and chrominance separation and a noise reduction.Color correction may be performed after the luminance and chrominanceseparation. By performing the noise reduction on the luminance data andthe chrominance data early after luminance and chrominance separation,the noise-increasing color correction generally has a smaller impact.Therefore, the luminance and chrominance noise reduction may be moreeffective, resulting in a higher quality final image.

In the step 122, an initial noise reduction (filter) may be performed onthe digital images received by the circuit 104 via the signal D. Thecircuit 104 may perform additional processing of the images byperforming a black level correction in the step 124, another noisereduction in the step 126, a white balance correction in the step 128and a noise reduction in the step 130. In the step 132, the digitalimages may be demosaiced to convert the picture information from a Bayerdomain to a red-green-blue (RGB) domain. An RGB noise reduction may beperformed in the step 134. A tone curve correction of the RBG images maybe performed in the step 136 by the circuit 104. Another RGB noisereduction may be performed in the step 138. In some embodiments, some toall of the noise reduction steps 122, 126, 130, 134 and 138 may beeliminated from the method 120.

The circuit 104 may convert the RBG images into a YUV (e.g., luminanceand chrominance) color space in the step 140. Both chrominancecomponents (e.g., U and V) of the image may be subject to chrominancenoise reduction by the circuit 104 (e.g., circuit 111 a) in the step142. The luminance components (e.g., Y) of the image may undergoluminance noise reduction in the circuit 104 (e.g., circuit 111 b) inthe step 144. Generally, the step 142 filters the chrominance componentsmore heavily than the step 144 filters the luminance components. Otherluminance and chrominance noise reduction techniques may be implementedto meet the criteria of a particular application.

In the step 146, the circuit 104 (e.g., circuit 111 c) may perform a YUVto YUV color correction on the filtered images. Since the step 146occurs after the luminance and chrominance noise reductions steps 142and 144, the color correction step 146 may induce less color-based noisethan common techniques. Steps 142 and 144 may be performed either inparallel by different circuits 111 a-111 n or sequentially by one ormore of the circuits 111 a-111 n. After the color space conversion, thecircuit 104 may compress the images in the step 148 for subsequentstorage in the circuit 108. Temporary storage of full and/or partialimages and associated data may utilize the circuit 106.

Referring to FIG. 6, a functional block diagram of an example imageprocessing method 160 is shown in accordance with a preferred embodimentof the present invention. The method (or process) 160 may be generallyimplemented by the apparatus 100, and in particular, by the circuit 104.The method 100 generally comprises the step 122, the step 124, the step126, the step 128, the step 130, the step 132, the step 134, the step136, the step 138, the step 140, the step 142, the step 144, the step148, a step (or block) 162, an optional step (or block) 164 and a step(or block) 166.

The method 160 may be similar to the method 120 with a primary colorcorrection (e.g., step 162) performed by the circuit 104 before theluminance and chrominance separation (e.g., step 138). An optional RGBnoise reduction may be performed in the step 164 between the primarycolor correction and the tone curve correction. A secondary colorcorrection (e.g., step 166) is generally performed by the circuit 104after the luminance and chrominance separation. In some embodiments, thestep 166 may perform the same color correction as the step 146. In otherembodiments, the step 166 may perform a different color correction thanthe step 146 to account for the changes already made by the primarycolor correction. The method 160 may be useful where noise addition (inthe circuit 102) and noise reduction (in the circuit 104) change thefinal color, compared with a case of low noise sensing and subsequentlow noise reduction. The secondary color correction generally restoresmore accurate colors to the final images.

Referring to FIG. 7, a functional block diagram of an example imageprocessing method 180 is shown. The method (or process) 180 may begenerally implemented by the apparatus 100. The method 100 generallycomprises the steps 122 to 138 (not shown), the step 140, the step 142,the step 144, the step 148, a step (or block) 182, an optional step (orblock) 184, a step (or block) 186 and a step (or block) 188.

The method 180 may be similar to the methods 120 and/or 160, andgenerally continues after the compression step. While the apparatus 100is operating in a recording mode, the compressed images may be writtenby the circuit 104 into the circuit 108 in the step 182. While operatingin a playback mode, the circuit 104 may read the compressed images fromthe circuit 108 in the step 184. In the step 186, the compressed imagesmay be decompressed by the circuit 104. A YUV to YUV lookup colorcorrection may be performed in the step 188 to establish video correctedcolors. The step 188 processing generally converts the images into oneor more formats suitable to present to a monitor via the signal VIDEO.While the apparatus 100 is operating in a viewing mode, the circuit 104may route the color corrected images created by the step 146 to the step186 so that a user of the apparatus 100 may see what the camera seeswithout consuming storage space in the circuit 108.

In some embodiments, the YUV to YUV color correction steps 146, 166and/or 186 may implement a lookup-table based correction method. Thelookup-table based correction method is generally described inco-pending U.S. application Ser. No. 12/706,816 and Ser. No. 12/712,307,both of which are incorporated by reference in their entirety.

The functions performed by the diagrams of FIGS. 4-7 may be implementedusing one or more of a conventional general purpose processor, digitalcomputer, microprocessor, microcontroller, RISC (reduced instruction setcomputer) processor, CISC (complex instruction set computer) processor,SIMD (single instruction multiple data) processor, signal processor,central processing unit (CPU), arithmetic logic unit (ALU), videodigital signal processor (VDSP) and/or similar computational machines,programmed according to the teachings of the present specification, aswill be apparent to those skilled in the relevant art(s). Appropriatesoftware, firmware, coding, routines, instructions, opcodes, microcode,and/or program modules may readily be prepared by skilled programmersbased on the teachings of the present disclosure, as will also beapparent to those skilled in the relevant art(s). The software isgenerally executed from a medium or several media by one or more of theprocessors of the machine implementation.

The present invention may also be implemented by the preparation ofASICs (application specific integrated circuits), Platform ASICs, FPGAs(field programmable gate arrays), PLDs (programmable logic devices),CPLDs (complex programmable logic device), sea-of-gates, RFICs (radiofrequency integrated circuits), ASSPs (application specific standardproducts) or by interconnecting an appropriate network of conventionalcomponent circuits, as is described herein, modifications of which willbe readily apparent to those skilled in the art(s).

The present invention thus may also include a computer product which maybe a storage medium or media and/or a transmission medium or mediaincluding instructions which may be used to program a machine to performone or more processes or methods in accordance with the presentinvention. Execution of instructions contained in the computer productby the machine, along with operations of surrounding circuitry, maytransform input data into one or more files on the storage medium and/orone or more output signals representative of a physical object orsubstance, such as an audio and/or visual depiction. The storage mediummay include, but is not limited to, any type of disk including floppydisk, hard drive, magnetic disk, optical disk, CD-ROM, DVD andmagneto-optical disks and circuits such as ROMs (read-only memories),RAMs (random access memories), EPROMs (electronically programmableROMs), EEPROMs (electronically erasable ROMs), UVPROM (ultra-violeterasable ROMs), Flash memory, magnetic cards, optical cards, and/or anytype of media suitable for storing electronic instructions.

The elements of the invention may form part or all of one or moredevices, units, components, systems, machines and/or apparatuses. Thedevices may include, but are not limited to, servers, workstations,storage array controllers, storage systems, personal computers, laptopcomputers, notebook computers, palm computers, personal digitalassistants, portable electronic devices, battery powered devices,set-top boxes, encoders, decoders, transcoders, compressors,decompressors, pre-processors, post-processors, transmitters, receivers,transceivers, cipher circuits, cellular telephones, digital cameras,positioning and/or navigation systems, medical equipment, heads-updisplays, wireless devices, audio recording, storage and/or playbackdevices, video recording, storage and/or playback devices, gameplatforms, peripherals and/or multi-chip modules. Those skilled in therelevant art(s) would understand that the elements of the invention maybe implemented in other types of devices to meet the criteria of aparticular application.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention.

The invention claimed is:
 1. An apparatus comprising: a circuitconfigured to (i) convert a digital image from a red-green-bluerepresentation to a luminance-and-chrominance representation, (ii)generate a reduced noise representation of said digital image byreducing noise in said luminance-and-chrominance representation, (iii)generate a color corrected representation of said digital image in saidluminance-and-chrominance representation by first color correcting saidreduced noise representation, wherein said first color correcting mapssaid reduced noise representation from a first color space to a secondcolor space in three dimensions, and (iv) generate another colorcorrected representation of said digital image in saidluminance-and-chrominance representation by second color correcting saidcolor corrected representation as read from a memory.
 2. The apparatusaccording to claim 1, wherein said first color correcting of saidreduced noise representation is an initial color correction of saiddigital image after being received from an electro-optical sensor. 3.The apparatus according to claim 1, wherein said circuit is furtherconfigured to convert said digital image from a Bayer color filter arrayrepresentation to said red-green-blue representation.
 4. The apparatusaccording to claim 1, wherein said circuit is further configured tosecond color correct said digital image prior to said reducing of saidnoise in said luminance-and-chrominance representation.
 5. The apparatusaccording to claim 1, wherein said circuit is further configured tocompress said color corrected representation of said digital image. 6.The apparatus according to claim 1, wherein said circuit is furtherconfigured to (i) noise filter a luminance component of saidluminance-and-chrominance representation of said digital image by afirst method and (ii) noise filter a chrominance component of saidluminance-and-chrominance representation of said digital image by asecond method, wherein said second method is a heavier filtering thansaid first method.
 7. The apparatus according to claim 1, wherein saidcircuit is further configured to store said digital image in a memoryafter said first color correcting.
 8. The apparatus according to claim1, wherein said apparatus forms a digital camera.
 9. The apparatusaccording to claim 1, wherein said luminance-and-chrominancerepresentation of said digital image comprises a YUV colorrepresentation of said digital image.
 10. A method for reducing noise ina digital image, comprising the steps of: (A) converting said digitalimage from a red-green-blue representation to aluminance-and-chrominance representation using a circuit; (B) generatinga reduced noise representation of said digital image by reducing noisein said luminance-and-chrominance representation; (C) generating a colorcorrected representation of said digital image in saidluminance-and-chrominance representation by first color correcting saidreduced noise representation, wherein said first color correcting mapssaid reduced noise representation from a first color space to a secondcolor space in three dimensions; and (D) generating another colorcorrected representation of said digital image saidluminance-and-chrominance representation by second color correcting saidcolor corrected representation as read from a memory.
 11. The methodaccording to claim 10, wherein said first color correcting of saidreduced noise representation is an initial color correction of saiddigital image after being received from an electro-optical sensor. 12.The method according to claim 10, further comprising the step of:converting said digital image from a Bayer color filter arrayrepresentation to said red-green-blue representation using said circuit.13. The method according to claim 10, further comprising the step of:second color correcting said digital image prior to said reducing ofsaid noise in said luminance-and-chrominance representation.
 14. Themethod according to claim 10, further comprising the step of: generatinga compressed representation of said digital image by compressing saidcolor corrected representation of said digital image.
 15. The methodaccording to claim 10, further comprising the steps of: noise filteringa luminance component of said luminance-and-chrominance representationof said digital image by a first method; and noise filtering achrominance component of said luminance-and-chrominance representationof said digital image by a second method, wherein said second method isa heavier filtering than said first method.
 16. The method according toclaim 10, further comprising the step of: storing said digital image ina memory after step (C).
 17. The method according to claim 10, whereinsaid method is performed in a digital camera.
 18. An apparatuscomprising: means for converting a digital image from a red-green-bluerepresentation to a luminance-and-chrominance representation; means forgenerating a reduced noise representation of said digital image byreducing noise in said luminance-and-chrominance representation; meansfor generating a color corrected representation of said digital image insaid luminance-and-chrominance representation by first color correctingsaid reduced noise representation, wherein said first color correctingmaps said reduced noise representation from a first color space to asecond color space in three dimensions; and means for generating anothercolor corrected representation of said digital image saidluminance-and-chrominance representation by second color correcting saidcolor corrected representation as read from a memory.